controlrod slop in big bird xl?

[balsabozo]

soooo close to maidening it kills me, but...

So I followed instructions for Ray Hayes' Big Bird XL (REF i did a mini thread on the flap and wing servos install). I opted for the steel wire control rods as he indicated it was the preferred method.

In my newbie ignorance I did not place any guide tubes between the bulkheads in the fuse. Ray didnt indicate any were needed, didnt really think about it either.

so now, covered in blue and yellow transparent monokote and in midst of programming and checking...
My buddy was over and noticed the slop, you can hear the wire bowing in the fuse for both elev and rudd. i split and glued tubes around the rods in the midsection of the fuse where i could get at throught the hatch.
I still have a lot of slop coming from bowing in the 2 remaining aft sections of the fuse between the bulkheads.

Need I be concerned on this plane? if so, how to address?
1. inject great stuff into fuse - i am worried the foam will stick to rod and not to fuse.
2. take a long copper tube, soder to a drill and snake it down from the aft end of fuse where the rods come out. then snake down same dia guide tubes and drizzle CA down to secure.
3. cry

[ThermalBuster]

Balsa,

You need to secure those rods so they can't bow. If you don't it will bite you.

Don't put expanding foam in the fuse. It will probably expand and bust the fuse wide open. It will be heavy in any case.

Going in and sliding a guide tube over the pushrods sounds feasible. Any other method you can think of to gain access might also be used. It is worth getting them tied down even if you have to cut an access slot in the top or bottom of the fuse from the wing saddle most of the way to the tail. Done carefully you may be able to put the piece back, recover and be good to go with almost no detectable marks.

Hope this helps
Rick







soooo close to maidening it kills me, but...

So I followed instructions for Ray Hayes' Big Bird XL (REF i did a mini thread on the flap and wing servos install). I opted for the steel wire control rods as he indicated it was the preferred method.

In my newbie ignorance I did not place any guide tubes between the bulkheads in the fuse. Ray didnt indicate any were needed, didnt really think about it either.

so now, covered in blue and yellow transparent monokote and in midst of programming and checking...
My buddy was over and noticed the slop, you can hear the wire bowing in the fuse for both elev and rudd. i split and glued tubes around the rods in the midsection of the fuse where i could get at throught the hatch.
I still have a lot of slop coming from bowing in the 2 remaining aft sections of the fuse between the bulkheads.

Need I be concerned on this plane? if so, how to address?
1. inject great stuff into fuse - i am worried the foam will stick to rod and not to fuse.
2. take a long copper tube, soder to a drill and snake it down from the aft end of fuse where the rods come out. then snake down same dia guide tubes and drizzle CA down to secure.
3. cry

[Andy W]

A couple of blocks of EPP foam wedged down the boom will hold it in place, if you're unable to glue it..
..a

[Liberator]

***BEWARE***

This will add some weight, but not a ton.

Go get some of these

http://www.sullivanproducts.com/GoldnRodContent.htm

You will want to use the nylon type. You can snake these into the fuse and secure them at either end with thin CA wicked down the outside of the tube.
Here is the easy way.

1. Leave the tubes long to start out.
2. Remove the inner sliding control rod.
3. Snake the outer guide rode into the fuse and align it where you want it.
4. Wick thin CA on the edge of the guide tube and hold the fuse nose down so the CA will run down the OUTSIDE of the tube.
5. Using a long stick or stiff wire make sure that tube tacks itself to the side of the fuse close to the servo side and also where it will exit near the tail surfaces.
6 Once it is tacked the way you want, you can cut it to length and insert the inner push rod. Keeping the outer rod long helps keep you from getting CA inside the tube which is pretty much the kiss of death.

THis will give you excellent positive control and take out all of the slop.

Tom

[balsabozo]

thanks for the advice guyz but...
there are 2 intervening bulkheads and the hole that allows the rods to pass are tiny. hence the need to bore them out if i try to feed something down the fuse and also the inability to stuff some epp down there.
any other sugg?

[Brian Kloft]

Get a sharp knife and perform plastic surgery. It will still look like new and your headache will be gone! :)

[apage]

Are the bulkheads balsa? What is the current size of the holes? What is the longest unsupported span that you cannot access?

[schrederman]

If the bulkheads are balsa, and the rods are wire, carefully notch the ends of the nylon tubes to resemble a hole saw and use the steel rods as a guide. It takes some doing but it works well. With the steel rods as a guide, you can even open the exits in the fuselage sides if you want.

Jack

[davidjensen]

Its time to cut into the outer skin and do what you need and replace the skin and recover. It should only take an hour or so. Since it's balsa its too easy. I know it's not going to make it look as good as it was but it will take care of the problem.

[Riserflier]

Whatever you do, get it flyable for the SASS Wood Wings '07 (part two) contest on Sunday August 5th.

[GliderDriver45]

I feel your pain!

The same thing happened when I built my Big Bird last year. The solution: 1) cut Rectangles out of the bottom of your Fuse about mid way between the bulkheads with a Dremel cutoff wheel. (poke a pin in the middle of the piece before you complete the cuts so you can hold onto the piece when the cut is completed and remove it with out having to fish it out of the Fuse) Take a small, 1.5 cm x 1.5 cm piece of 3/32 or 1/8 ply and cut a 1/16 wide by 1/16 deep groove on one side. ( I did this using the edge of my perma-grit F100 sander.) 3) apply small dab of medium CA to the wood next the the groove. Carefully place the groove over the push rod wire. 4) hold the wooden guide in place against the fuse side and move the control surface with your hand till the CA cures to keep any stray CA from binding your control rod to the guide. 5) Repeat process between each bulk head and on each control rod. 6) Glue the rectangle ( you still have the pin in it right?) back in the hole you cut it out of with thin CA by pushing it snug against 2 of the cut surfaces. Then fill the remaining gap on the other two edges with baking soda or balsa dust and apply ca to fill the joint. 7) sand gently and apply patch of your covering.

Just another possible solution.

I never got to step 7 but the problem was fixed and the plane flew great till I tried to winch launch it with my radio set to the wrong model. Spectacular nose dive in after it popped off. Fuse survived intact. one wing half broke at the dihedral break. Very fixable.



By the way you will love the way the plane flies. My Big Bird was my favorite plane till the "hard landing" put it in the repair hanger.

Greg

[balsabozo]

ok, so i dug up a narrow brass tube about 3ft in length and used it as a bore, managed to snake it down and widen the holes in the bulkheads. just wanted to see if it were possible. as unluck would have it, it was too narrow for even the narrowest plastic rod in my shop.

even if i do get down to central welding supply tomorrow am, will the flexible plastic rods do it? i'll need to somehow glue them in place to really make them work, yes? trickling ca down the tube sounds iffy, as i wonder if it'll hit the first bulkhead and occlude that and go no further. 1 way would be to estimate where they lay in the fuse and poke a few pinholes on the sides of the fuse and then ca those holes.

[rabidrue1]

Schrederman has the cure. Heres how ive done this before-notch up out side caseing to resemble a hole saw. Take some 60 grit sand paper and sand outer rod lenthwise, you want long stright scratches in it. Cut outer rod 3" or so longer than you need. Slip a dowel in one end of tube-1"long or so. Clamp the dowel filled end in youre cordless drill. have somebody hold the fuse for you. Useing current wire rod for a guide slowley spin and feed outer tube in to fuse right up to the servo arm. Remove the old wire push rod and trim the tube to lenth. Drill a 1/16" hole in rear of fuse righr up against the outer tube-follow the outsidewall of the tube with the bit. Hold fuse nose down and with the skinny tube attached to youe thin ca bottle slowley drip in the ca. Make another 1/16" hole at the sero end bulk head also right next to outer tube and drip ca from that end. The scratches in the outside of the tube will help leed the ca from end to end and dripping from both ends seals the deal. I have had this work with a lenth of 45" and had every thing stuck niceley. IT WASNT THE GULE BOND OF THE ELEVATOR PUSH ROD TUBE THAT WAS CAUSE FOR POST MORTOM EXAM IT WAS MY DUMB THUMBS. All kidding aside that nyrod caseing was stuck to all 6 bulkheads and crossmembers that it passed thru and was mostly what was holding the bag of balsa I picked up together

[balsabozo]

fixed!

for benefit of others:
- 0.014 thickness 3ft brass tubing, 7/32dia.
- took a no 11 exacto and at 1 end of tube "cored" out so that it was a little sharper/thinner (trick from Scobie of Lyftworx).
- chocked up the brass on my drill directly and wha-la! gently bevel-drilled the fuse at the aft end (not totally pretty , but heck!) and broke thru the 3 bulkheads real fast.
- pulled out the tube and fed thru the outer tubing from a nylon rod set.

right now, there is only slop from the most proximal part of the rod next to arms on servo where i can fiddle with it

i'm still going to drizzle ca down the tube from both ends but Im not going to worry as much as to whether it sticks to fuse or not seeing as it stands there is little slop now in the intervening sections just by virtue of the nylon/plastic rod stiffness.

very cooll, thanks for all suggestions! (incl spiritquest, esp for catching the problem to being)

[Dave Moore]

I'm building an Oly III and when I fitted the wire pushrods supplied by Ray, the friction was horrendous! Besides, Ray makes you solder two wires together to make the rod long enough. I substituted Sullivan 48" pushords. With these the friction was so minimal that the problem was the rod kept sliding out of the sheath as I manipulated the fuse.

And to keep it on topic, I glued the sheath to the sides of the fuse.

I have heard that the nylon rods will change length with temperature. Sullivan claims it's minimal but provides no specs. I know that steel will expand and contract with temperature as well. Also, the real goal is to have the expansion of the rod equal the expansion of the fuse.

Just rambling here. I've got what I've got and I'll see how it works.

BlueSky Dave

[davidjensen]

We are all hoping to see your new ship fly this wednesday.